Hamidreza Mahani

School of Astronomy, Institute for Research in Fundamental Sciences (IPM)

Exploring Stellar Populations

Abstract: Understanding the luminosity of unresolved stellar populations is recognized as a crucial aspect of galaxy evolution studies. This presentation will address how detailed information from resolved stellar populations is leveraged to infer the physical properties of unresolved populations through stellar population synthesis (SPS) models. A key focus will be placed on the role of the initial mass function (IMF) and the impact of dust in shaping the observed luminosity. By bridging theoretical frameworks with observational data, models can be refined to enhance the interpretation of the luminosity of distant, unresolved populations. Recent advancements in SPS modeling will be presented, demonstrating how the incorporation of IMF and dust properties facilitates the extraction of meaningful insights regarding the composition and evolution of galaxies. This approach is posited as a powerful framework for understanding the interplay between stars and their environment in both nearby and high-redshift galaxies.

یکشنبه 7 اردیبهشت 1404، ساعت 15:00

Sunday 27 April 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­تئاتر – تالار جناب Physics Department – Amphitheatre– Jenab Hall  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Saeed Ansarifard

School of Physics, Institute for Research in Fundamental Sciences (IPM)

Hunting for Dark Matter in Jupiter 

Abstract: The particle nature of dark matter (DM) remains unresolved, with viable models spanning keV to TeV scales. Within the ‘DM as particles’ paradigm, neutrino experiments provide critical sensitivity to DM interactions—but celestial bodies like Jupiter may offer complementary probes. I will discuss DM capture and annihilation in massive astrophysical objects, demonstrating how Jupiter’s high gravitational potential and low background could generate a detectable flux. Crucially, I will highlight how the orbital superposition of Jupiter and the Sun enhances this signal’s visibility, potentially revealing sub-GeV DM annihilation products. This approach opens a new pathway to constrain DM properties beyond terrestrial experiments.

یکشنبه 31 فروردین 1404، ساعت 15:00

Sunday 20 April 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­ تئاتر – تالار جناب /Physics Department – Amphitheatre– Jenab Hall   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Discussion Session on DESI results

Coordinated by

Yashar Akrami

Instituto de Física Teórica (IFT) UAM-CSIC, Madrid, Spain,

CERCA/ISO, Department of Physics, Case Western Reserve University, USA,

Astrophysics Group & Imperial Centre for Inference and Cosmology, Department of Physics, Imperial College London, UK

Abstract: In this session, we will have a discussion coordinated by Yashar Akrami on the Dark Energy Spectroscopic Instrument (DESI) new results and its cosmological implications.

The main paper is https://arxiv.org/abs/2503.14738

The list of papers can be found in URL: https://data.desi.lbl.gov/doc/papers

یکشنبه 24 فروردین 1404، ساعت 15:00

Sunday 13 April 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­تئاتر – تالار جناب Physics Department – Amphitheatre– Jenab Hall   /

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Farshid Gholami

Department of Physics, Sharif University of Technology

A review based on two papers:

1. A. C. Fabian; “Observational Evidence of AGN Feedback”

2. Andrew King, Ken Pounds; “Powerful Outflows and Feedback from Active Galactic Nuclei”

Abstract: This talk is based on two papers:

1-    Observational Evidence of AGN Feedback A. C. Fabian

https://arxiv.org/abs/1204.4114

Annual Review of Astronomy and Astrophysics Volume 50, 2012

2-    Powerful Outflows and Feedback from Active Galactic Nuclei Andrew King, Ken Pounds

https://arxiv.org/abs/1503.05206

Annual Review of Astronomy and Astrophysics Volume 53, 2015

یکشنبه 19 اسفند 1403، ساعت 15:00

Sunday 9 March 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­تئاتر – تالار جناب Physics Department – Amphitheatre– Jenab Hall   /

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Shant Baghram

Department of Physics, Sharif University of Technology,

Research Center for High Energy Physics, Department of Physics, Sharif University of Technology

In Search of Extraterrestrial Artificial Intelligence Through Dyson Sphere–like Structures around Primordial Black Holes*

Abstract: Are we alone? It is a compelling question that human beings have confronted for centuries. The search for extraterrestrial life is a broad range of quests for finding simple forms of life up to intelligent beings in the Universe. The plausible assumption is that there is a chance that intelligent life will be followed by advanced civilization equipped or even dominated by artificial intelligence (AI). In this work, we categorize advanced civilizations (on an equal footing, an AI-dominated civilization) on the Kardashev scale. We propose a new scale known as the space exploration distance to measure civilization advancement. We propose a relation between this length and the Kardashev scale. Then, we suggest the idea that advanced civilizations will use primordial black holes (PBHs) as sources of harvesting energy. We calculate the energy harvested by calculating the space exploration distance. Finally, we propose an observational method to detect the possibility of extraterrestrial AI using Dyson sphere–like structures around PBHs in the Milky Way and other galaxies. (Based on Shant Baghram, 2025 ApJ 978 132)

*This work is dedicated to Sohrab Rahvar, whom we admire for first teaching us about life in the Universe.

یکشنبه 12 اسفند 1403، ساعت 15:00

Sunday 2 March 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­تئاتر – تالار جناب /Physics Department – Amphitheatre– Jenab Hall   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Elahe Khalouei

Astronomy Research Center, Research Institute of Basic Sciences, Seoul National University

Multi-Messenger Research at the Center for the Gravitational-Wave Universe

Abstract: In this presentation, we will begin with a brief review of South Korea’s in-kind contributions to major projects such as LSST and SPHEREx, as well as their plans to develop a multi-system telescope for future competition (~ 6 min).

 Next, we will cover the following topics:

1-    The observation of strongly lensed supernovae using a 7-dimensional telescope (~20 min).

2-    Key definitions related to gravitational waves (~10 min).

3-    If time permits, the application of deep learning in gravitational wave studies (~10 min).

یکشنبه 5 اسفند 1403، ساعت 15:00

Sunday 23 February 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی­ تئاتر – تالار جناب /Physics Department – Amphitheatre– Jenab Hall   

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Mohammad Hossein Namdar

Department of Physics, Sharif University of Technology

Cosmological Structure Formation in Monge-Ampère Gravity 

Abstract: The Monge-Ampère gravity is a novel and effective mathematical theory in the formation of cosmic structures, proposed with the aim of generalizing classical Newtonian gravity. This theory is based on the Monge-Ampère equation, a nonlinear version of the Poisson equation that relates the determinant of the Hessian of the potential to the density field. We precisely demonstrate how the Poisson equation can be derived from the Monge-Ampère equation in the weak field limit. Subsequently, we analytically solve the equation for a point mass density distribution under the assumption of spherical symmetry. We further investigate structure formation in the presence of this gravity and determine the critical density required for structure formation using the spherical collapse approximation in both linear and nonlinear regimes. Finally, we examine the statistics of the halos formed under this gravity. Although we consider Monge-Ampère gravity as an effective rather than a fundamental theory in this study, we compare our results with the solutions of the Poisson equation in all cases.

یکشنبه 28 بهمن 1403، ساعت 15:00

Sunday 16 February 2025 – 15:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – آمفی ­تئاتر – تالار جناب Physics Department – Amphitheatre– Jenab Hall  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Zeinab Kalantari

Department of Physics, Sharif University of Technology,

Research Center for High Energy Physics, Department of Physics, Sharif University of Technology

A Study of Cosmological Models Based on Long Gamma-ray Bursts Duration Histogram

Abstract: In this presentation, I want to speak about the idea of constraining the cosmological model by the long GRBs’ duration data of the Swift-BAT satellite. Gamma-ray bursts’ powerful luminosity enables us to explore the universe at the farthest redshift reaches ever explored. The maximum observable redshift of gamma-ray bursts is estimated to be around $z=9.4$, so GRBs could serve as an excellent tool to investigate the characteristics of the cosmos at high redshifts, such as constraining the cosmological parameters such as dark energy equation of state. The burst duration $T_{90}$ is a significant property of GRBs that can be analyzed. In my presentation, I focus on comparing the histogram of long GRBs’ duration resulting from a kind of $ \omega CDM$ cosmological model with an energy equation of state, $P= c \omega(z) \rho$ and a $\Lambda CDM$ model. I considered a cosmological model for $\omega(z)=-1 +\alpha z$ then I tried to find the best $\alpha$. In this paper, we first calculate the detection rate of Swift/BAT for a cosmological model with the $ \omega CDM$ model. We use this probability density function to generate the redshift of LGRBs in our Monte-Carlo simulation. in a Monte Carlo simulation, we want to simulate $\tau = \tau_0 (1+z)$ for 1347 mock LGRBs and compare the histogram of $\tau$ for assumed cosmological model and observational histogram of $\tau$. Finally, $\chi^2$ minimization method is employed to determine the optimal value of $\alpha$ in the dark energy equation of state, $P= c \omega(z) \rho$, with $\omega(z)=-1+\alpha z$ . We showed that for the $\omega CDM$ model all values of $\alpha$ within $\alpha=[0, 0.16]$ range are considered acceptable within two standard deviations.

یکشنبه  16 دی 1403، ساعت 17:00

Sunday 5 January 2025 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3 /  

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Arefeh Alizadeh

Department of Physics, Sharif University of Technology

Dark Matter Phenomenology: Production Mechanisms and Freeze-In via Inverse Semi-Annihilation

 Abstract: Dark matter is a key part of modern cosmology and particle physics. Studying its evolution and properties helps us understand the universe’s large-scale structure, galaxy dynamics, and the fundamental particles that may exist beyond the Standard Model.

In this presentation, I will give an overview of the evidence supporting the existence of dark matter and the possible candidates proposed to explain these observations. Production mechanisms, including misalignment, thermal freeze-out, and freeze-in, will be discussed. I will then focus on the freeze-in mechanism, a well-motivated scenario for non-thermal dark matter production. As discussed in arXiv:2104.05684, through inverse semi-annihilation processes, the freeze-in mechanism can explain the current abundance of dark matter. The semi-production approach allows for larger coupling values compared to the usual freeze-in scenario by considering a small initial abundance of dark matter.

یکشنبه 9 دی 1403، ساعت 17:00

Sunday 29 December 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3  / 

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest

Adeela Afzal

Department of Physics, Quaid-i-Azam University, Islamabad, Pakistan

Tracing the Cosmos with Stochastic Gravitational-Wave Background

Abstract: Hybrid inflation provides a rich framework for understanding the early universe’s dynamics and its connection to observable cosmic structures. This talk will explore the role of hybrid inflation in generating topological defects and the stochastic gravitational wave background, emphasizing model-building approaches to connect theoretical predictions with observations. I will discuss the potential origins of the signals detected in the NANOGrav 15-year dataset and how they relate to cosmic phenomena such as scalar-induced gravitational waves and cosmic strings. Furthermore, we will delve into the intriguing possibility of primordial black hole formation during hybrid inflation and its implications for current and future astrophysical observations.  I will also talk about weighted Morphology and its implications on topological defects. This presentation aims to bridge theoretical insights with observational data, shedding light on the intricate interplay between inflationary physics, gravitational waves, and primordial black holes.

یکشنبه 18 آذر 1403، ساعت 17:00

Sunday 8 December 2024 – 17:00 Tehran Time

Hybrid Seminar

دانشکده فیزیک – طبقه اول – کلاس فیزیک 3 Physics Department – first floor – Room Physics 3 /  

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest